Skip to main content

Full text of "Text Book Of Mechanical Engineering"

See other formats


858

Appendix II.

Hodgkinson's results for hollow round W. I. columns, co-ordinates
being/and r, as on p. 459. As the plottings scarcely approach
the Euler curve, the problem is to find what curve will suit.
Gordon's curve G with a = 16 and b = -^y^ evidently strikes an
average, which he intended it should. Fidler objects to this
treatment, holding that the curve should be made to fit the lower
or worst results, and he has therefore devised a formula, too
complicated for regular use, and shewn by curve F F. Apparently,

WROUGHT   IRON   PILLARS   :     EM PS

   EuJL&r Cu.rv& .   *26toooooo

FF    fAJcULer   CuLTUCf   fxt&aU to Lou/er

G G     CrOrdLoTLf C&tJ'UC,          OL,    16         1} s  jtooo

9    Cordon, Curve,         cc,-   fj      b ~ lofco

Fig. 820.

however, a judicious alteration of Gordon's constants should
approach Fidler's curve, for when a = 17 and b = ^5^ line gg
is drawn; but if a = 14 and b = T^9 the lower and safer line
hh is obtained. Another way is to take /some 80 or 85% of
Gordon, which would meet the experience of engineers.

P. 461. Combined Torsion and Bending. We shall
here shew how the two stresses ft and j are combined into one
equivalent stress fc. If a pair of shear stresses Fx F1? Fig. 821, act
on an imaginary solid A BCD, within a structure, they cannot